[Networkmanager] NetworkManager link local IPv4 address based on last 2 octets of ethernet MAC address

[manjunatha srinivasan]

Hi
I have 2 following ethernet profiles
at /etc/NetworkManager/system-connections:
One for dynamic ip configuration and other for link local as fallback when
DHCP server is not reachable. As expected when DHCP server is not
reachable, fall back IPv4 address happens e.g. 169.254.105.20 with subnet
mask as 255.255.0.0 by the NetworkManager.
This particular IP address is always the same which is expected one.
Please let me know how this constant IPv4 address is decided by the
NetworkManager. Also let me know if there is any configuration option in
NetworkManager to change last 2 octets (i.e.105.20) represented in the
decimal value of last 2 values of ethernet MAC hex address.

*Ethernet (eth0) method based on DHCP:*
[connection]
id=my-eth0
uuid=8466b654-0183-4900-a2d6-26a9e6af275e
type=ethernet
autoconnect-priority=1
interface-name=eth0
timestamp=1697699281

[ethernet]

[ipv4]
dhcp-timeout=10
method=auto

[ipv6]
addr-gen-mode=stable-privacy
method=auto
ra-timeout=10

[proxy]
-------------------
*Ethernet (eth0) method based on link-local:*
root at FXR90D5FB72:/etc/NetworkManager/system-connections# cat
 rfid-ll-eth0.nmconnection
[connection]
id=ll-eth0
uuid=f07f43e6-59c8-428f-bc04-55a0e581e621
type=ethernet
interface-name=eth0

[ethernet]

[ipv4]
method=link-local

[ipv6]
addr-gen-mode=stable-privacy
method=auto

[proxy]
------

When DHCP request fails, the IPv4 address fallback to



Thanks & Regards
Manjunatha Srinivasan N
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